To provide a low cement soil conditioner in which the utilization of previously developed high activity cement is attempted, and a large amount of porous and water absorbent inorganic scrap that are worry for disposal are used, thereby responding to the soil improvement of a high water content soil generated in a construction site.

The soil conditioner includes: 10-60 wt.% of high activity cement of high C₃S and ultra low C₂S that comprises adding gypsum to high activity cement clinker in which the mineral composition of a calculated value by a vogue formula is C₃S>70% and C₂S<5%, L.S.D. exceeds 1, and the amount of free lime is 0.5-7 wt.%; and 40-90 wt.% of inorganic powder granular material of porosity incineration ash or the like that has water absorbent power because there are microvoids.